This invention relates to a control valve for an air conditioning for a motor vehicle air conditioning system. The valve according to the invention is particularly applicable to air conditioning systems of the type comprising a compressor which pressurizes a refrigerant fluid, such as Freon 12, in a condenser, and an evaporator or expansion device in which the fluid is allowed to expand in thermal exchange relationship with the passenger compartment of the vehicle.
In air-conditioning systems of the aforesaid type it is known to provide a valve for controlling the flow of refrigerant fluid: this valve is arranged to cut off, or restrict, the flow of fluid when the thermodynamic conditions of the said fluid are such as to prejudice proper functioning of the system. One such control valve is described in the Applicants' Italian Pat. No. 952850. The valve described in that Patent, whilst achieving its intended purpose, is such that it cannot operate to shut off or restrict the flow of refrigerant fluid; it operates only in the event of increased pressure in the system. Therefore, as improvements and better performances are continually being achieved for air-conditioning systems, it is necessary to provide a control valve which operates in response to several parameters, involving the thermodynamic state, not only of the air-conditioning system itself, but also of the passenger compartment, or even in response to direct manual intervention.
An object of the present invention is to provide a control valve which can be operated in response to one or a number of interdependent parameters.